Journal Article

Differences in seasonal expression of flowering genes between deciduous trifoliate orange and evergreen Satsuma mandarin

Fumie Nishikawa, Tomoko Endo, Takehiko Shimada, Hiroshi Fujii, Tokurou Shimizu and Mitsuo Omura

in Tree Physiology

Volume 29, issue 7, pages 921-926
Published in print July 2009 | ISSN: 0829-318X
Published online July 2009 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpp021
Differences in seasonal expression of flowering genes between deciduous trifoliate orange and evergreen Satsuma mandarin

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To determine differences in seasonal flowering between evergreen and deciduous woody perennials, endogenous expression of flowering-related genes was investigated in Satsuma mandarin (Citrus unshiu Marc.) and its close relative, trifoliate orange (Poncirus trifoliata (L.) Raf.), which are evergreen and deciduous, respectively, and show different seasonal flowering characteristics. In Satsuma mandarin, in which floral induction is triggered by low temperatures during fall and winter, mRNA levels of the citrus FLOWERING LOCUS T homologue CiFT increased during fall and winter, corresponding to the floral induction period, and mRNA levels of citrus LEAFY and SEPALLATA homologues (CsLFY and CuSEP) increased during early spring just before blooming. Citrus APETALA1 and FRUITFULL homologues (CsAP1 and CuFUL) did not show a significant association with seasonal flowering. In trifoliate orange, in which floral induction and flower bud development occur during early summer as in many deciduous trees, expression of CiFT, CsLFY, CsAP1, CuSEPs and CuFUL increased during early summer, corresponding to the period of floral induction and flower bud development. The CuSEPs expression peaked again during early spring just before blooming. In both species, the citrus TERMINAL FLOWER1 homologue (CsTFL), which acts as a floral repressor, showed low transcript levels during the period of floral induction and flower bud development. Thus, despite the difference in flowering season, in both species transcriptional changes in CiFT, CsLFY, CsTFL and CuSEPs were correlated with seasonal flowering. In contrast, the correspondence between CsAP1 and CuFUL expression and seasonal flowering differed between the species.

Keywords: citrus; Citrus unshiu; floral induction; floral repressor; flower bud development; FT; Poncirus trifoliate; seasonal flowering

Journal Article.  3074 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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